Monthly Archives: June 2022

June 24, 2022

Subseasonal Weather Outlook (27 June – 10 July 2022)

Issued: 24 June 2022
First forecast week: 27 June – 3 July
Second forecast week: 4 July – 10 July

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over much of the southern half of the Maritime Continent in the next fortnight (27 June – 10 July). Wetter conditions are also expected over northern Mainland Southeast Asia and northern Philippines in Week 1 (27 June – 3 July).

Warmer than usual temperatures are expected over the southeastern Maritime Continent in the next fortnight (27 June – 10 July). Warmer than usual temperatures are also expected over southern Mainland Southeast Asia in Week 1 (27 June – 3 July) and predicted to persist over southeastern Mainland Southeast Asia in Week 2 (4 – 10 July).

In the third week of June, there were signs of a Madden-Julian Oscillation (MJO) signal in the Indian Ocean (Phase 2) based on the RMM Index. Most models predict an MJO signal to develop and propagate eastwards through the Indian Ocean (Phases 2 and 3) in Week 1. Some models predict the MJO signal to continue propagating eastwards through the Maritime Continent (Phases 4 and 5) in Week 2.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

June 17, 2022

Review of Regional Weather for May 2022

1. Overview

1.1 During May 2022, near- to above-average rainfall was recorded over much of the northern ASEAN region, while a mixture of below- to above-average rainfall was recorded over the southern ASEAN region (Figure 1). For the northern ASEAN region, the largest positive anomalies in rainfall (wetter conditions) were recorded over the southern Myanmar for both satellite-derived rainfall estimates datasets (GSMaP-NRT and CMORPH-Blended). For the southern ASEAN region, above-average rainfall was recorded over central Indonesia and a mix of below- to above-average elsewhere. The two datasets agree well over most of the ASEAN region. However, there are some discrepancies over western Borneo and southern Sumatra where CMORPH recorded below- to near-average rainfall whereas GSMaP-NRT recorded near- to above-average rainfall.

1.2 The observed rainfall anomaly pattern of above-average rainfall for parts of the northern ASEAN region, particularly Myanmar, is broadly consistent with the predictions from the subseasonal weather outlooks for May 2022 (2 – 15 May and 16 – 29 May). The drier conditions predicted over the equatorial region for 16 – 29 May, can be observed over parts of the western and eastern equatorial region, although overall in May it was relatively wet over the central equatorial region.

Figure 1: Rainfall anomalies for the month of May 2022 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2021. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 Most parts of northern ASEAN region recorded below-average temperature in May 2022 (Figure 2). The largest negative anomalies (2°C cooler than normal conditions for May) were over northeastern Thailand and northern Viet Nam. For most of the southern ASEAN region, normal to above-average temperature were recorded with largest warm anomalies over Peninsular Malaysia and southeastern Indonesia.

Figure 2: Temperature anomalies for the month of May 2022 based on ERA-5 reanalysis. The climatological reference period is 2001-2021. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 There was no discernible Madden-Julian Oscillation (MJO) signal at the start of May 2022 based on the MJO phase diagram below (Figure 3). In the first week of May, an MJO signal emerged over the Indian Ocean (Phase 2). For the second week of May, the MJO signal first became relatively weaker as it moved eastwards over the Indian Ocean (Phase 3). This signal then strengthened again and continued moving rapidly eastwards over the Maritime Continent (Phase 4 and 5) and Western Pacific (Phase 6). In the third week of May, the signal moved further east over the Western Pacific (Phase 7) and Western Hemisphere (Phase 8), before weakening and becoming indiscernible. Towards the end of May, an MJO signal emerged again over the Western Pacific (Phases 6 and 7). For the central Maritime Continent, Phases 3, 4, and 5 can all bring wetter conditions, while for the western Maritime Continent, Phases 6 and 7 tend to bring drier conditions. Therefore, the MJO may have contributed to the wetter conditions over parts of the central Maritime Continent and drier conditions over parts of the western Maritime Continent during May.

Figure 3: The MJO phase diagram. The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator (denoted in the text with the first day of the month in blue and the last day of the month in red). The distance of the index from the centre of the diagram is related to the strength of the MJO. Values within the grey circle are considered weak or indiscernible (data from the Bureau of Meteorology, Australia).

2.2 Over the tropical Pacific Ocean, La Niña conditions were present. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) and the atmospheric indicators over the tropical Pacific Ocean were consistent with La Niña conditions. La Niña events tend to bring wetter-than-average conditions to much of Southeast Asia during the March to May period. Over the Indian Ocean, there were signs of a negative Indian Ocean Dipole developing in May but the Dipole Mode Index (DMI), which is used to measure the Indian Ocean Dipole (IOD) signal, remained neutral. Negative IOD tends to bring wetter-than-average conditions for much of Southeast Asia.

June 16, 2022

Review of Regional Haze Situation for May 2022

1.1 Inter-monsoon conditions started to give way to Southwest Monsoon conditions through May 2022 as the monsoon rainband continued to move northwards over the northern ASEAN region. The prevailing winds over the ASEAN region blew generally from the southeast or southwest, except for regions close to the Equator where winds were light and variable in direction (Figure 1).

1.2 Rainy weather was observed over most of the ASEAN region in May 2022 although drier conditions prevailed over the Lesser Sunda Islands and the northernmost parts of the Mekong sub-region. Heavy rainfall was observed in parts of southern Philippines, as well as the southern parts of both Myanmar and Thailand (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for May 2022. (Source: JAXA GsMaP and GFS, respectively)

1.3 For May 2022, the total number of hotspots were lower or comparable to previous years for the same period (Figures 2 and 3), except in Sumatra and Kalimantan where a slightly higher number of hotspots were detected in May 2022 compared to previous years.

Figure 2: Hotspot counts for the southern ASEAN region for the month of May (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

Figure 3: Hotspot counts for the northern ASEAN region for the month of May (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

1.4 Isolated to scattered hotspots (Figures 4 and 5) and moderate smoke haze (Figure 6) were observed in the first week of May 2022 over northern parts of the Mekong sub-region. However, the onset of wetter conditions over the northern ASEAN region in subsequent weeks helped to suppress hotspot and smoke haze activities here. As wet conditions became established, the Alert Level over the Mekong sub-region was downgraded to Alert Level 1 on 10 May 2022, and the End of Dry Season (Alert Level 0) was declared on 19 May 2022.

1.5 The hotspot and smoke haze situation in the southern ASEAN region remained subdued as rainy conditions continued to prevail. Isolated hotspots were detected (Figures 4 and 5) and localised smoke plumes were observed to emanate from some of these hotspots in Borneo and the central Sumatra on some days.

Figure 4: Distribution of hotspots detected in May 2022 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in May 2022 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense smoke haze observed in May 2022 based on satellite imagery, ground observations, and air quality reports.

June 10, 2022

Subseasonal Weather Outlook (13 – 26 June 2022)

Issued: 10 June 2022
First forecast week: 13 June – 19 June
Second forecast week: 20 June – 26 June

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For rainfall, wetter conditions are expected over much of the southern ASEAN region in the next fortnight (13 – 26 June). Drier conditions are expected over southern Mainland Southeast Asia in Week 1 (13 – 19 June).

For temperature, cooler than usual temperatures are expected over much of the western and central equatorial region in the next fortnight (13 – 26 June).

A Madden-Julian Oscillation (MJO) signal was present in the Western Hemisphere and Africa (Phases 8 and 1) in the second week of June based on the RMM Index. Most models predict this MJO signal to decay in Week 1 with no significant MJO activity for the rest of the forecast period.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

June 3, 2022

18th ASEAN COF (May 2022, Online)

Eighteenth Session of the ASEAN Climate Outlook Forum (ASEANCOF-18)

24 and 26 May 2022, PAGASA

Consensus Bulletin for June-July-August (JJA) 2022 Season

The ASEAN Climate Outlook Forum (ASEANCOF) is an avenue to collaboratively develop consensus-based seasonal climate outlooks and related information on a regional scale. The forum’s outlook and its activities contribute significantly to one of the key roles of the ASEAN Specialised Meteorological Centre (ASMC), which is to conduct climate and seasonal prediction for the Association of Southeast Asian Nations (ASEAN) region through pooling the expertise of ASEAN National Meteorological and Hydrological Services (NMHSs). In 2021, the ASEANCOF Working Group was established with the goal to guide and support the long-term development of ASEANCOF, in particular with regard to the implementation of objective outlooks.

The Eighteenth session of ASEANCOF (ASEANCOF-18) was organised by the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) in collaboration with the ASMC and the ASEANCOF Working Group. Participants from the NMHSs of ASEAN Member States created a consensus forecast for the boreal summer monsoon 2022 in the ASEAN region. The consensus for June-July-August (JJA) 2022 outlook was achieved through an online session, which included presentations from different NMHSs, questionnaires, and discussions regarding the current climate conditions and predictions in the Southeast Asia region. In particular, ASEANCOF considered the influence of the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the climate system over Southeast Asia. There was also a special focus on monsoon variability, with a presentation from the Regional Working Group on Asian-Australian Monsoon (AAM-WG).

Conditions and Outlook

Recent analyses of sea surface temperature (SST) anomalies over the equatorial Pacific show below average SSTs across the central and eastern tropical Pacific Ocean indicative of La Niña. The international climate outlooks predict that the La Niña is likely to weaken during JJA 2022, although still overall indicate La Niña conditions. After JJA 2022, most models predict the ENSO state to be either cool ENSO neutral or La Niña.

The current IOD state is neutral. Most models predict a negative IOD developing during JJA 2022, with some models predicting the said negative IOD to be strong.

The onset of the Southwest Monsoon season has been earlier than normal in many parts of Mainland Southeast Asia, and near normal in the Maritime Continent. Over much of Southeast Asia, the strength of the Southwest Monsoon is expected to be near normal or weaker than normal, based on model predictions.

Overall, the tropical cyclone frequency is expected to be near average in the Bay of Bengal, while below to near average around the South China Sea and in the Philippine Sea. As there is an expected weakening of La Niña in JJA 2022, no significant deviation from the climatology of tropical cyclone frequency is expected during the forecast period.

Taking into consideration the national level forecasts, the present state of the climate, and the forecasts available from the global prediction centres (GPCs), the ASEANCOF-18 agreed on the following consensus-based outlook for JJA 2022 in the ASEAN region:

RAINFALL

Over much of the southern ASEAN region, near to above normal rainfall is predicted. Near to above normal rainfall is predicted over Brunei Darussalam and many parts of Malaysia, with above normal rainfall predicted most elsewhere. The exceptions include parts of the western and eastern Maritime Continent, where near to below normal rainfall is predicted.

Over much of the northern ASEAN region, a mix of below to above normal rainfall is predicted. Near to below normal rainfall is predicted over the western and southeast portion of Mainland Southeast Asia, and northwest Philippines. Near to above normal rainfall is predicted over portions of northeast and southern Mainland Southeast Asia, and southern Philippines. Elsewhere in the northern ASEAN region, near normal rainfall is predicted.

TEMPERATURE

Near to above normal temperature is predicted over the ASEAN region. The highest likelihood of above normal temperature is over the southern Maritime Continent and Lao PDR, while near normal temperature is predicted over northern Myanmar, northern and central Viet Nam, and parts of the western Maritime Continent. An equal chance of near to above normal temperature is predicted over southern Myanmar, Thailand, Cambodia, southern Viet Nam, the Philippines, Malaysia, and Brunei Darussalam.

Refer to Annex A for reference on what is meant by “above, near, or below normal” in the outlook. For more information on the boreal (Northern Hemisphere) summer monsoon outlook and further updates on the national scale, the relevant NMHSs should be consulted (see Annex B).

Consensus Maps for JJA 2022 Season

The following maps provide the probabilistic outlooks for JJA 2022 season in terms of tercile categories of “Above Normal” (AN: upper tercile), “Near Normal (NN: middle tercile) and “Below Normal” (BN: lower tercile).

PROBABILISTIC RAINFALL OUTLOOK

PROBABILISTIC TEMPERATURE OUTLOOK

Meeting Documents

ASEANCOF-18 Outlook Bulletin

Acknowledgements

ASEANCOF would like to convey its appreciation to the NMHSs of the ASEAN Member States for sharing their national level forecasts, the GPCs, the Southeast Asia Regional Climate Centre – Network, and other partners of ASEANCOF for sharing their products and expertise, and the World Meteorological Organization Regional Office in Asia and the Southwest Pacific (WMO-RAP) for their continued support of ASEANCOF.